The invention relates to the field of transportation of oil products, especially heavy and extra heavy oil products and, particularly, to a conduit for such transportation which has an inner surface which inhibits adhesion of heavy and extra heavy oil products to the flow surface of the conduit.
Heavy and extra heavy oil is available in abundant supply and is suitable for numerous uses. Such heavy and extra heavy oil must usually be transported to distant consumption centers, however, which causes problems due to the viscous nature of the oil.
Numerous methods for transporting heavy and extra heavy oil have been disclosed, such as reducing viscosity of the oil with diluents and/or heat, providing oil in water dispersions and/or emulsions, and forming oil/water systems having the oil in a substantially stable core surrounded by a sleeve or substantially annular flow of water.
Heating and diluent processes are expensive. Oil/water systems are also problematic as the oil tends to adhere to pipeline and tubing walls upon contact with them, thus leading to restriction and eventual blockage of the flow system. Such problems are exacerbated where flow must be stopped for a period of time, allowing stratification of the oil and water phases and increased adhesion of the oil. Restarting the flow in such a stopped system may require a large pressure, even possibly exceeding the pressure rating of some or all components of the flow system. Such problems also necessitate the washing of the flow system to remove adhered oil, causing additional expense and down time of the flow system.
One known method for preventing adhesion of oil to flow surfaces of conduits in oil/water systems is to add salts such as silicates, borates, carbonates, sulfates, phosphates, and the like to the system water. Such addition of salt is discussed, for example, in U.S. Pat. No. 3,977,469 to Broussard et al. dealing with oil/water core flow as mentioned above. The addition of salt to the system water appears to help in reducing adhesion of oil to the conduit. However, the effects of the salt additive decrease with time as the salt is removed from the system by reaction with the oil, and also during periods of stopped flow where the water at least partially stratifies, allowing contact of the oil with the flow surfaces of the conduit and, thus, adhesion. Further, the added salt is an additional ingredient and, thus, an additional source of cost in the oil transportation process.
It is the principal object of the present invention to provide a conduit having an inner flow surface which substantially prevents the adhesion of oil.
It is a further object of the invention to provide such a conduit wherein the prevention of adhesion of heavy and extra heavy oil products does not decrease with time.
It is yet another object of the invention to provide a process for transporting crude oil in a flow system having conduits according to the invention which have an inner flow surface which substantially prevents the adhesion of 0:1, whereby the crude oil is more efficiently and cost effectively transported.
Other objects and advantages will appear hereinbelow,